This invention relates to an apparatus for exchanging lead and trail edges of sheets, and more particularly, to an improved gateless rocker sheet inverting inverter apparatus that alternately engages sheets with two roller nips in order to drive sheets in opposite directions.
Although a sheet inverter is referred to in the copier/printer art as an "inverter", its function is not necessarily to immediately turn the sheet over (i.e., exchange one face for the other). Its function is to effectively reverse the sheet orientation in its direction of motion. That is, to reverse the lead and trail edge orientation of the sheet. In typical inverters, the sheet is driven or fed by feed rollers or other suitable sheet driving mechanisms into a sheet reversing chute. By then reversing the motion of the sheet within the chute and feeding it back out from the chute, the desired reversal of the leading and trailing edges of the sheet in the sheet path is accomplished. Depending on the location and orientation of the inverter in a particular sheet path, this may or may not also accomplish the inversion (turning over) of the sheet. In some applications, for example, where the "inverter" is located at the corner of a 90.degree. to 180.degree. inherent bend in the copy sheet path, the inverter may be used to actually prevent inverting of a sheet at that point, i.e., to maintain the same side of the sheet face-up before and after this bend in the sheet path. On the other hand, if the entering and departing path of the sheet, to and from the inverter, is in substantially the same plane, the sheet will be inverted by the inverter. Thus, inverters have numerous applications in the handling of either original documents or copy sheets to either maintain or change the sheet orientation.
In the field of reprographic machines, it is often necessary to feed a copy sheet leaving the processor of the machine along one of two alternate paths, particularly when the machine can selectively produce simplex (one-sided) and duplex (two-sided) sheets. Simplex sheets may be fed directly to an output tray, whereas the duplex sheets may pass to a sheet feeder which automatically reverses the direction of movement of a simplex sheet and feed it back into the processor, but inverted, so that the appropriate data can be applied to the second side of the sheet. One known sheet-feeder (U.S. Pat. No. 4,359,217) for effecting this includes three rollers in frictional or geared contact with each other, to provide two spaced-apart nips, one being an input nip to an associated downstream sheet pocket, and the other being an output nip for extracting each sheet from the pocket.
The present invention aims at providing an inverter designed to have a sheet to be duplexed fed to it, stopped momentarily, and fed back to a processor for imaging onto the opposite side. The inverter includes two nip pairs with drive rolls continuously rotating. Idler rolls that mate with the drive rolls to form the two nips are adapted to swing between engagement and disengagement positions with one nip set moving a sheet in a forward direction and the other nip set moving the sheet in a reverse direction.